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Help select suitable Mosfet for driving relay.

Discussion in 'Microcontrollers, Programming and IoT' started by HellasTechn, Apr 27, 2019.

  1. hevans1944

    hevans1944 Hop - AC8NS

    Jun 21, 2012
    That sounds like an excellent idea! I had forgotten about out discussion vis a vis the counterfeit MAXIM MAX232 back in 2016.

    Not to hijack this thread, but this topic of counterfeit Asian parts came up in the Flashlight thread when the OP purchased a counterfeit PICkit 3 programming pod for his PIC microprocessor. Fortunately, he was able to return it and get his money back, but who needs that kind of trouble? I have run into a similar problem with counterfeit RS-232-to-USB converters. These are legitimately made in Taiwan using a chip designed there, but counterfeits from mainland China abound. Some work, but later software drivers would "brick" those chips if the software "discovered" their use. When I purchased, about a year ago, a converter module (my laptop PC has no serial ports) I bought it from Amazon and have had no problems with it.
  2. Bluejets


    Oct 5, 2014
    Yes, that was another story and if I remember that particular mob was forced to pull it's head in and issue a fix for it's deliberate actions.
  3. HellasTechn


    Apr 14, 2013
    Should i add a gate resistor to make sure that no current will go back to the microcontroller in case the mosfet fails ?
  4. Bluejets


    Oct 5, 2014
    You can, many do.

    However it's not to stop any current flow back into the micro.

    It is to limit the micro pin current.

    I think the usual value is around 120 ohm.
    HellasTechn likes this.
  5. Minder


    Apr 24, 2015


    May 20, 2017
    MOSFETS are susceptible to parasitic oscillation. The is due to any pcb track or wire inductance that can cause a series resonant circuit in conjunction with the gate - source capacitance which can precipitate oscillation of the Fet. A resistor in series with the gate forms a low pass pole which should negate this effect.
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